Does anyone have any opinions on which if these packages is better for the beginner user for modeling centrifugal turbomachinery?

(1). In response to your e-mail, even though I have given you the recommendation about the code which I think is more widely used in pumps and fans, it is still a good idea to visit each vendor's website to get more samples related to your applications. (2).Radial turbomachinery is highly 3-D, and the flow field always involves flow separation even under the design conditions. (3). It is also a good idea to read the ASME/ Journal of Turbomachinery. You should be able to find some published CFD papers related to the radial turbomachinery.(centrifugal pumps and fans)

Sam, I think it is too hard to answer this type of question and I don't think that there is a reliable answer at all. To answer your question you should try to use these codes for solving the same problem and compare its outcome with experimental results.